Contact structure



Aug. 26, 1958 R. E. FRlNK CONTACT STRUCTURE 4 Sheets-Sheet 1 Filed July 31, 1956 INVENTOR Russell E. Frink.

"4 ATTORNEY Fig wmusssas Aug. 26, 1958 Filed July 31, 1956 R. E. FRINK CONTACT STRUCTURE 4 Sheets-Sheet 2 Aug. 26, 1958 R. E. FRINK 2,849,579

CONTACT STRUCTURE Filed July 31, 1956 4 SheetsSheet 5 Aug. 26, 1958 R. E. FRINK CONTACT STRUCTURE 4 Sheets-Sheet 4 Filed July 31, 1956 Fig. 6.

(IONTACT STRUCTURE Russell E. Frink, Forest Hills, Pa... assignor to Westinghouse Electric @orporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 31, 11 56, fierial No. 601,259

11 Claims. (Cl. zen-44s This invention relates to circuit breakers and more particularly to contact structures for air circuit breakers.

An object of the invention is to provide a circuit breaker embodying an improved contact structure that is compact and has high current-carrying capacity.

Another object of the invention is to provide a circuit breaker embodying an improved contact structure having high interrupting and current-carrying capacities which is of rugged and durable construction.

Another object of the invention is to provide a circuit breaker with an improved contact arrangement according to the preceding paragraphs wherein the magnetic forces induced by the current flow are utilized to increase the contact pressure.

Other objects and advantages of the invention will be pointed out in the following description and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In said drawings:

Figure l is a side elevational view showing the improved contact structure in the closed-contact position.

Fig. 2 is an enlarged elevational view of the stationary contact structure taken along line IIII of Fig. 1 and looking in the direction indicated by the arrows and partly broken away for clearness.

Fig. 3 is a bottom View of the stationary contact structure shown in Fig. 2.

Fig. 4 is an enlarged vertical sectional View of the contact structure taken on line IVIV of Fig. 2, showing the contacts in the position at which the main contacts are about to separate.

Fig. 5 is an enlarged elevational view of the contact structure showing the contacts in full lines in the position at which the intermediate contacts are about to separate,

and in dot-and-dash lines in the position at which the arcing contacts are about to separate.

Fig. 6 is a perspective view of the contact block for supporting the stationary contact assembly.

The invention is illustrated as applied to a circuit breaker of the type disclosed in Patent No. 2,717,292, issued September 6, 1955, to Russell E. Frink and Paul Olsson and assigned to the assignee of the present invention.

The circuit breaker shown in the aforementioned patent is of the roll-out type and is mounted on a wheeled truck to facilitate rolling the breaker into and out of a cubicle in order to connect and disconnect the breaker in an electrical circuit. The circuit breaker is provided with a rigid frame for supporting the elements of the circuit breaker.

The contact structure comprises generally a stationary contact assembly 11 rigidly mounted on the inner end of an upper terminal 13 which is rigidly supported on the framework (not shown) of the breaker, and a movable switch arm 15 pivotally supported on a lower terminal 17 also rigidly supported on the breaker frame.

The movable switch arm 15 is pivotally mounted by a pivot pin 19 on the lower terminal 17 and is electrically connected to the terminal 17 by means of a flexible con- 2,849,573 Fatented Aug. 26, 1958 ductor 20. The movable switch arm 15 is operatively connected by means of an insulating operating rod 21 to a suitable operating mechanism which may be of the type disclosed in the above-mentioned patent, and which is more fully disclosed in Patent No. 2,515,994, issued July 18, 1950, to Joseph D. Findley, Alvin W. Ogg and Fritz E. Florschutz, to which reference may be had for a full and complete understanding of the operating mechanism.

The movable switch arm 15 has rigidly mounted there-- on a plurality of laterally spaced main movable contacts 23, a movable intermediate contact 25 and a movable arcing contact 27. The main movable contact 23 cooperates with spaced main stationary contact assembly indicated generally at 29. The movable intermediate contacts 25 cooperate with a stationary intermediate contact 31, and the movable arcing contact 27 cooperates with a stationary arcing contact 33. The stationary intermediate contact 31 and the stationary arcing contact 33 are mounted on a contact platform 35 supported on an upper contact block indicated generally at 37 for limited movement relative thereto by means of a pair of spaced plates 39 disposed one on each side of the contact block 37.

The contact block 37 comprises a heavy plate member 41 rigidly secured to the upper terminal 13 by any suitable means that will provide a good mechanical and electrical connection such as by welding or brazing. In the same manner there is attached to the inner face of the plate member 41 a contact support member 43 which is formed to provide three spaced, vertical support bars 415, 47 and 49 (Fig. 6). The plates 39 are supported on the outsides of the vertical bars and 49 by means of bolts or studs 51 and 5'3 which extend through openings in the plates 39 and openings in the vertical bars 45, 4-7 and 49. The bolts or studs 51 and 53 are threaded at both ends to receive nuts 55.

The stationary contact assembly 29 comprises outer contacts 57 rigidly secured to the lower inner portions of the plates 39 (Figs. 2 and 3) and extending toward each other. A pair of inner main stationary contacts 59 are rigidly secured to the lower inner ends of L-shaped contact-carrying members or plates 61. The inner main stationary contacts also extend from their respective members 61 toward each other. The L-shaped members 61 are pivotally supported at their upper ends on the bolt 51 and the bolt 53 passes through openings in the members 61 that are slightly larger than the diameter of the bolt to permit individual alignment of the contacts.

The plates 39 are pressed against the outer faces of the support bars 45 and 49 by means of springs 63 compressed between the nuts and washers 65 adjacent the plates 39 to provide good contact pressure between the plates 39 and the contact block. Similarly the contact carrying members 61 are biased against opposite sides of the center support bar 47 by springs 67 disposed inside of the springs 63 and compressed between the nuts 55 and bushings or sleeves 69 which surround the bolts 51 and 53 and bear against the members 61. In order to provide good electrical contact between the contact support members 61 and the bar 47, washers 71 of a good conducting material such as silver are mounted on the bolt 51 between the members 61 and the bar 47. For the same purpose the lower portions of the center bar 4-7, where the contact members 61 bear against it, are heavily plated with a material of high conductivity such as silver, as indicated at 73 (Fig. 2). The openings 75 in the outer bars 45 and 49 and the opening 77 in the center bar 47 through which the bolt 53 passes are larger than the diameter respectively of the sleeves 69 and the bolt to permit limited main contact follow when the movable switch arm 15 moves in opening direction.

The plates 3% are biased in a clockwise direction about the upper bolt 51 by means of springs 79 (Fig. 3) compressed between the contact members 57 and the sup port plate 41 to provide contact pressure in the closed position and contact follow when the breaker opens. The outerends of the springs 79 are seated in counterbores 81 in the contact members 57 and the plates 39 to which the contact members 57 are brazed. Spring guides 83 in the form of screws are provided to retain thesprings in position on the plate 41, The inner contact carrying members 61 and the contact members 59 brazed thereto are biased in a clockwise direction about the upper bolt 51 by a pair of springs 85 (Figs. 3 and 4) having one end seated in a counterbore 87 in the face of the center bar 47. The other ends of the springs 85 bear against a washer 89 which bears against a pressure equalizing member 91. The equalizer 91 is angular in form and the opposite ends bear against the contact members The washer 89 is provided with a spring guide 93 on one side and a projection 95 on the opposite side which fits in an opening in the equalizer 91 to hold the parts in position.

The platform 35 is generally U-shaped and is provided with studs 97 (Fig. extending laterally in opposite directions from the side portions thereof. The studs 97 engage in elongated slots 99 in the plates 39 to support the platform for limited movement relative to the plates 39. Ears 101 extend laterally from the sides of the platform 35 into openings 103 in the plates 39 to limit the movement of the platform.

The contact platform 35 is biased outwardly away from the contact support block 37 by means of a pair of concentric coil springs 105 (Fig. 4) disposed adjacent the upper end of the platform 35 and a pair of spaced coil springs 107 (only one being shown) located at the lower end of the platform. The springs 105 are compressed between the center support bar 47 and the contact platform 35. The springs 105 are seated in a counterbore 109 in the center support bar 47 and are provided with a guide stud 111 secured to the support bar 47. A flexible conductor 113 is provided to electrically connect the contact platform 35 to the contact block 47. The flexible conductor 113 is generally U-shaped and one end is secured by bolts 115 (only one being shown) to the lower portion of the platform 35. The other end of the flexible conductor 113 is secured to the support bars 45, 47 and 49 by a clamp 117 which is secured to the support bars 45, 47 and 49 by means of screws 119 thus clamping the flexible conductor to the bars. The springs 107 (onlyone being shown) are compressed between the end of the flexible conductor 113 adjacent the platform 35 and the clamp 117. A washer 121 is disposed between the spring 107 and the clamp 117 and is provided with a spring seat 123 on one side and a locating projection 125 on the other side. The locating projection 125 extends into an opening in the clamp member 117 between the screws 119 to hold the washer 121 and the spring seat 123 in proper position. The end of the spring 107 adjacent the platform 35 surrounds the head of the bolt 115 which acts as a spring guide.

When the movable switch arm 15 moves in opening direction under the influence of the operating mechanism disclosed in the aforementioned Patents No. 2,717,292 and No. 2,515,994, the stationary main contacts 5759, the stationary intermediate contact 31 and the stationary arcing contact 33 remain in contact respectively with their corresponding moving contacts 23, 25 and 27 until the sleeves 69 surrounding the lower bolt 53 engage the walls of the openings 75 in the outer support bars 45 and 49 and the bolt 53 engages the opening 77 in the center support bar 47, the plates 39 pivoting about the upper bolt 51'by the force of the springs 79 and the contact carrying members 61 pivoting about the upper bolt 51 by the force of the spring 85. The contact structure is shown in Fig. 4 in the position at which the main contacts are about to separate. In this position the move- 4 ment of the plates 39 and the contact carriers 61 has been arrested but the contact platform 35 has followed the movable switch arm under the influence of the springs and 107. In the Fig. 4 position the studs 97 on the platform 35 have not reached the ends of the slots 99 in the plates 39 and the ears 101 have not engaged the walls of the openings 103 in the plates 39. The plates 39 and the contact levers 61 do not move farther during the opening movement of the switch arm 15, but upon continued movement of the switch arm in opening direction, the platform 35 follows until the studs 97 engage the left end of the slots 99. At this point the main contacts have separated slightly as shown in Fig. 5 and the intermediate and arcing contacts are still engaged. The parts are shown in this position in full lines in Fig. 5.

As the opening movement of the switch arms 15 continues, the platform 35 pivots about the studs 97 and the upper end thereof follows the switch arm with the arcing contact 33 maintaining contact with the moving arcing contact 27 until the ears 101 engage the walls of the openings in the plates 39. In this position of the parts, shown by dot-and-dash lines in Fig. 5, the main and intermediate contacts have separated to the positions shown and the arcing contacts are about to separate.

Upon continued opening movement of the switch arm 15 the arcing contacts separate and the switch arm will move to the full open position without further movement of the stationary contact structure drawing an are between the arcing contacts, the arc being drawn into an arc-extinguishing structure, indicated generally at 127 (Fig. 1), where it is quickly extinguished.

The contacts close in the reverse sequence when the switch arm 15 is operated to the closed position, that is, the arcing contacts close first, then the intermediate contacts, and finally the main contacts close.

In the type of circuit breaker illustrated, the arc will usually be extinguished when the arcing contacts have separated approximately two inches. When interrupting capacitor banks or are furnaces, and under certain conditions when the circuit constants give a low damping factor and the current is of suflicient magnitude, a switching surge may be produced which will cause the arc to restrike across a gap of this dimension or larger. Such restrikes may even occur outside the arc chute between live or grounded parts such, for instance, as between the main stationary contact and the moving switch arm 15 at a point below the main movable contacts. The latter is prevented by providing the switch arms with an insulating shield or barrier 129 (Fig. 1).

The invention provides an improved contact structure which increases the momentary and continuous currentcarrying capacity in a small, compact contact arrangement which permits placing the entire separating contact structure inside the arc chute, hence, any restriking of the arc will occur between the interrupting contact structure and will be confined within the arc extinguisher.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts may be made without departing from some of the essential features of the invention.

I claim as my invention:

1. In a circuit breaker, a stationary contact structure comprising a fixed member having spaced inner and outer support members thereon, a pair of plates disposed on the outer side of each of said outer support members and pivotally mounted on said outer support members for limited movement relative thereto, spring means providing pressure contact between said plates and said outer support members, contact-carrying members disposed between said outer support members and said inner support member and pivotally mounted on said support members for limited movement relative thereto, spring means providing pressure contact between said contact-carrying members and said inner support member, main stationary contact means on said plates andon said contact-carrying members, a contact member disposed between said pivoted plates and supported between said plates for limited movement relative thereto, intermediate and arcing contacts on said contact member, and a movable switch memher having movable main, intermediate and arcing con tacts thereon for cooperating respectively with said stationary main, intermediate and arcing contacts to open and close the circuit.

2. In a circuit breaker, a stationary contact structure comprising a fixed contact support having a plurality of spaced contact support members thereon, contact-carrying members disposed between said spaced inner and outer contact support members, contact-carrying plates disposed on the outsides of the outer contact support members, main stationary contact on said contact-carrying members and on said contact-carrying plates, pivot means pivotally supporting said contact-carrying members and said contact-carrying plates for limited movement relative to said contact support members, spring means providing pressure contact between said contact-carrying members and said inner contact support members, other spring means providing pressure contact between said contact-carrying plates and outer contact support members, a contact mem ber supported by said pivoted plates for limited movement relative thereto, intermediate and arcing contacts on said contact members, and a movable switch arm having movable main, intermediate and arcing contacts thereon cooperating respectively with said stationary main, intermediate and arcing contacts to open and close the circuit.

3. in a circuit breaker, a stationary contact structure comprising a fixed contact support having a plurality of spaced contact support members thereon, contact-carrying members disposed between the spaced inner and outer contact support members and biased for limited movement relative thereto, contact-carrying plates disposed on the outsides of the outer contact support members and biased for limited movement relative thereto, main stationary contact on said contact-carrying members and on said contact-carrying plates, pivot means pivotally supporting said contact-carrying members and said contact-carrying plates for limited pivotal movement relative to said contact support members, spring means providing pressure contact between said contact-carrying members and said inner contact support members, other spring means providing pressure contact between said contactcarrying plates and outer contact support members, a contact member supported by said pivoted plates for limited movement relative thereto, intermediate and arcing contacts on said contact member, and a movable switch arm having movable main, intermediate and arcing contacts thereon cooperating respectively with said stationary main, intermediate and arcing contacts to open and close the circuit.

4. In a circuit breaker, a contact structure comprising a fixed conducting member, a pair of spaced contact plates pivotally mounted one on each side of said conducting member and biased for limited movement relative to said conducting member, a plurality of contact levers pivotally mounted between said contact plates on said conducting member and biased for limited movement relative to said conducting member, main stationary contacts rigid with said contact plates and said contact levers, spring means biasing said contact plates and said contact levers into pressure engagement with said conducting members, a rigid contact member having stationary intermediate and arcing contacts thereon, said rigid contact member being mounted on said pivotally mounted contact plates and biased for limited movement relative to said contact plates and said conducting member, and a movable switch arm having movable main, intermediate and arcing contacts rigid therewith cooperating with said stationary contact structure to open and close the circuit.

In a circuit breaker, a pair of spaced terminals, a

stationary contact structure comprising a conducting member rigidly mounted on one of said terminals, means defining a plurality of channels in said conducting member, a plurality of contact levers one mounted in each of said channels and biased for limited movement relative to said conducting member, a pair of contact plates pivotally mounted on each side of said conducting member for limited movement relative thereto, stationary contacts rigid with said contact levers and said contact plates, spring means biasing said contact levers in opposite directions into pressure engagement with said conducting members, spring means biasing said contact plates in opposite directions into pressure engagement with said conducting members, a rigid contact member mounted on said pivotally mounted contact plates and biased for limited movement relative to said contact plates and said conducting member, and a movable switch member pivotally mounted on the other of said terminals cooperating with said stationary contact structure to open and close the circuit.

6. In a circuit breaker, a pair of spaced terminals, a stationary contact structure comprising, a conducting member rigidly mounted on one of said terminals, means defining a plurality of channels in said conducting member, a plurality of contact levers one mounted in each of said channels and biased for limited movement relative to said conducting member, a pair of pivoted contact plates mounted on each side of said conducting member for limited movement relative thereto, main stationary contacts rigid with said contact levers and said contact plates, spring means biasing said contact levers and said contact plates for moving said main stationary contacts away from said stationary conducting member, spring means biasing said contact levers in opposite directions into pressure engagement with said conducting member, spring means biasing said contact plates in opposite directions into pressure engagement with said conducting member, a rigid contact member mounted on said pivoted contact plates and biased for limited movement relative to said pivoted contact plates and said conducting member, and a'movable switch member pivotally mounted on the other of said terminals cooperating with said stationary contact structure to open and close the circuit.

7. In a circuit breaker, a pair of spaced terminals, a member of conducting material mounted on one of said terminals, 21 pair of outer contact-carrying members having openings therein and disposed one on each side of said conducting member, a plurality of inner contactcarrying members, each of said contact-carrying members having main contacts rigid therewith, pivot means pivotally mounting all of said contact-carrying members on said conducting member for movement relative thereto, means for limiting the movement of said contact-carrying members relative to said conducting members, springs biasing said outer and inner contact-carrying members into close engagement with said conducting members, a rigid contact member disposed between said pivotally mounted outer contact-carrying members and having intermediate and arcing contacts rigid therewith, a plurality of projections on said rigid contact member engaging the openings in said pivotally mounted outer contactcarrying members to support said rigid contact members between said outer contact-carrying members for movement relative thereto and for limiting said movement, a pivoted switch arm pivotally supported on the other of said terminals and having movable main, intermediate and arcing contacts rigid therewith, said switch arm being movable to open and closed positions to effect engagement and disengagement of said movable contacts with the corresponding stationary contacts.

8. in a circuit breaker, a stationary contact structure comprising fixed support means having a slot therein, a first contact-carrying member mounted on the side of said support means, a second contact-carrying member mounted in said slot, a stud extending through openings in said support means and said contact-carrying members supporting said contact-carrying members for movement relative to said support means, a bushing surrounding said stud in the openings in said second contact-carrying member and one portion of said support member, said bushing bearing against the contact-carrying member mounted in said slot, a pair of springs, one of which applies a pressure contact between said first contactcarrying member and the side of said one portion of said support means, and the other of said spring applying a pressure to said bushing to thereby provide a pressure contact between said second contact-carrying member and another portion of said support means.

9. In a circuit breaker, a stationary contact structure having spaced support members, a contact plate mounted on the outside of one of said support members, a contact member mounted between said spaced support members, a stud extending through openings in said support members, said contact plate and said contact members, a bushing surrounding said stud and disposed in said openings in said one support member and in said contact plate and bearing against said contact member, a pair of concentric springs surrounding said stud, one of said springs providing pressure contact between said contact plate and said one support member, and the others of said springs applying a force to said bushing to provide pressure contact between said contact member and the other of said support members.

10. In a circuit breaker, a stationary contact structure having spaced support members, a contact plate mounted on the outside of one of said support members, a contact member mounted between said support members, spaced studs extending through openings in said spaced support members, said contact plate and said contact member, one of said studs supporting said contact plate and said contact member for movement relative to said support members, the other of said studs limiting the movement of said contact plate and said contact members, bushings surrounding said studs and disposed in the openings in said one support member and in said contact plate, said bushings bearing against said contact member mounted between said support members, pairs of springs surrounding said spaced studs, one spring of each pair of springs providing pressure contact between said contact plate and said one support member in the area adjacent said spaced studs, and the other spring of each pair of springs applying a force to said bushings to I provide pressure contact between said contact member the other of said support members in the area adjacent said spaced studs.

11. In a circuit breaker, a stationary contact structure comprising an inner support member and outer support members spaced from said inner support member, contact plates mounted at the outsides of said outer support members, contact members mounted in the spaces between said support members, a stud extending through openings in said support members, said contact plates and said contact members movably supporting said contact plates and said contact members, bushings surrounding said stud and disposed in openings in said outer support members and in said contact plates and bearing against said contact members mounted between said support members, pairs of springs at opposite ends of said stud, one spring of each pairof springs providing pressure contact between said contact plates and the outer support members, and the other spring of each pair applying a force to said bushings to provide pressure contact between said contact members and opposite sides of said inner support member.

References {Iited in the file of this patent UNITED STATES PATENTS 1,967,623 Massey July 24, 1934 2,571,933 Olsson et al. Oct. 16, 1951 2,708,699 Jansson May 17, 1955 

